In the past, postoperative and post-trauma treatment of patients's joints commonly included immobilization. The affected joints were fixed by casts or traction for an extended duration. As a result of such immobilization various medical problems commonly arose. In particular, capsular, ligamentous and articular adhesions, thromboembolism, venos stasis, post-traumatic osteopenia, peripheral edema, muscle atrophy, and the like were commonly attributed to the immobilization.
It is now known that immobilization related medical problems could be reduced or eliminated by early mobilization of the affected joint. It has been found to be advantageous to initiate joint mobilization immediately following orthopedic surgery, in many instances in the operating and recovery rooms while the patient is still under anesthesia. Specifically, continuous passive motion of the affected joints have been found to be effective in reducing or eliminating the above-referenced medical problems, promoting faster healing, reducing the amount of pain and medications, improving the range of movement of the affected joint after recovery, and the like.
Continuous passive motion devices (CPMs) are typically motor driven and are designed to exercise a particular joint by repeatedly extending and flexing the joint. The CPMs are capable of applying continuous motion to the joint in a consistent manner and can be adjusted to operate at different speeds and within a defined range of motion. In such CPMs, it is important that the joint be anatomically aligned on the CPM. The limb is typically secured to a moveable carriage member which is driven by the motor. The carriage member includes a plate or other softgoods for directly receiving the limb. Straps or the like are used to secure the limb to the plate or softgoods.
Conventional CPMs are problematic in that the plate or softgoods for receiving the limb are rigidly secured to the carriage member. Thus, conventional CPMs cannot mechanically compensate for any misalignment of the patient's anatomical pivot points on the CPM. Therefore, conventional CPMs work in opposition to anatomical alignment causing the patient's leg to compromise its natural motion. A need has arisen for a carriage member which includes a plate for receiving the limb which is permitted to move with respect to the carriage member and thereby compensate for different sizes and shapes of various patients, misalignment due to the patient's leg shifting during therapy, or possible misalignment at initial setup by the therapist.
Other CPMs have drawbacks in that they lack the requisite amount of power to raise and bend a relatively heavy limb. Many patients, such as a football player or perhaps a short non-flexible patient, can easily exceed the lifting capacity of conventional CPMs. Presently, this problem has been addressed by a machine which includes a large double reduction gear head that is supported by an external stand attached to the frame of a hospital bed. This machine exceeds seventy-five pounds in weight and is hard to move from patient to patient. Consequently, a need has arisen for a CPM which has the requisite power required to raise and bend a relatively heavy limb without increasing the overall size and weight of the CPM.
Conventional indirect drive CPMs drive one end of the carriage member at a substantially constant velocity. Because of the typical triangular configuration formed between the carriage member and base of the indirect drive CPMs, moving one end of the carriage member at a substantially constant velocity results in an inconsistent angular velocity at the joint as it is repeatedly flexed and extended. Conventional CPMs are typically driven by electrically powered motors which have a speed that is directly proportional to the applied voltage and inversely proportional to the applied load. This usually results in speed variance that is inconsistent with patient comfort. Thus, a need has arisen for a CPM which can maintain constant angular velocity of the joint.
The present invention overcomes many of the disadvantages inherent in the above-described CPMs by providing a CPM which flexes the joint at a constant angular velocity and is capable of lifting relatively heavy limbs. The present invention is also capable of achieving consistent anatomical alignment by compensating for patients of varying size and shape, compensating for any misalignment due to the patient's leg shifting during therapy, and compensating for possible misalignment at initial setup by the therapist. Consequently, use of the present invention results in comfort to the patient as well as decreases the overall time necessary for rehabilitating the joint.